1ca0584345
published in https://reviews.facebook.net/D5997. Summary: This patch allows compaction to occur in multiple background threads concurrently. If a manual compaction is issued, the system falls back to a single-compaction-thread model. This is done to ensure correctess and simplicity of code. When the manual compaction is finished, the system resumes its concurrent-compaction mode automatically. The updates to the manifest are done via group-commit approach. Test Plan: run db_bench
97 lines
2.7 KiB
C++
97 lines
2.7 KiB
C++
// Copyright (c) 2012 Facebook.
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#ifndef STORAGE_LEVELDB_DB_MEMTABLELIST_H_
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#define STORAGE_LEVELDB_DB_MEMTABLELIST_H_
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#include <string>
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#include <list>
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#include "leveldb/db.h"
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#include "db/dbformat.h"
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#include "db/skiplist.h"
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#include "util/arena.h"
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#include "memtable.h"
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namespace leveldb {
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class InternalKeyComparator;
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class Mutex;
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class MemTableListIterator;
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//
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// This class stores refeernces to all the immutable memtables.
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// The memtables are flushed to L0 as soon as possible and in
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// any order. If there are more than one immutable memtable, their
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// flushes can occur concurrently. However, they are 'committed'
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// to the manifest in FIFO order to maintain correctness and
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// recoverability from a crash.
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//
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class MemTableList {
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public:
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// A list of memtables.
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MemTableList() : size_(0), num_flush_not_started_(0),
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commit_in_progress_(false) {
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imm_flush_needed.Release_Store(NULL);
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}
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~MemTableList() {};
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// so that backgrund threads can detect non-NULL pointer to
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// determine whether this is anything more to start flushing.
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port::AtomicPointer imm_flush_needed;
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// Increase reference count on all underling memtables
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void RefAll();
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// Drop reference count on all underling memtables
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void UnrefAll();
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// Returns the total number of memtables in the list
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int size();
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// Returns true if there is at least one memtable on which flush has
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// not yet started.
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bool IsFlushPending();
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// Returns the earliest memtable that needs to be flushed.
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// Returns null, if no such memtable exist.
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MemTable* PickMemtableToFlush();
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// Commit a successful flush in the manifest file
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Status InstallMemtableFlushResults(MemTable* m,
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VersionSet* vset, Status flushStatus,
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port::Mutex* mu, Logger* info_log,
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uint64_t file_number,
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std::set<uint64_t>& pending_outputs);
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// New memtables are inserted at the front of the list.
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void Add(MemTable* m);
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// Returns an estimate of the number of bytes of data in use.
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size_t ApproximateMemoryUsage();
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// Search all the memtables starting from the most recent one.
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// Return the most recent value found, if any.
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bool Get(const LookupKey& key, std::string* value, Status* s);
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// Returns the list of underlying memtables.
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void GetMemTables(std::vector<MemTable*>* list);
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// Copying allowed
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// MemTableList(const MemTableList&);
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// void operator=(const MemTableList&);
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private:
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std::list<MemTable*> memlist_;
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int size_;
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// the number of elements that still need flushing
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int num_flush_not_started_;
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// committing in progress
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bool commit_in_progress_;
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_DB_MEMTABLELIST_H_
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